Electric staplers accommodated inside, for example, a copying machine, a printing machine, or the like to bind a plurality of copied or printed sheets to be bound have been conventionally known. In such electric staplers, a driver unit for striking out a staple toward sheets, and a clincher unit for bending legs of a staple penetrated through sheets are vertically separated from each other and arranged to be spaced from each other, whereby sheets can pass between the respective units. In such electric staplers, after sheets are arranged between the respective units, the clincher unit is lowered toward sheets, as arranged in a bound position on a conveyance path whereby the sheets are clamped between the clincher unit and an upper surface of the driver unit, thereafter a driver of the driver unit is actuated to strike out a staple toward the clamped sheets. Thereafter, a clincher mechanism of the clincher unit is actuated to bend legs of the staple penetrated through the sheets along a back surface of the sheets so as to bind the sheets. Then, the respective units are driven to return to home positions separated from each other (see, for example, JP-A-09-136302).
In order to avoid a problem that respective drive mechanisms become complex and an apparatus becomes large in size because one drive motor drives a driver unit and a clincher unit with the use of a cam mechanism, a linkage, etc., JP-A-09-136302 discloses an electric stapler, which is made simple in mechanism and can be made small in size by providing exclusive drive motors on a driver unit and a clincher unit, respectively, using the drive motor of the driver unit to drive a driver, and using the drive motor of the clincher unit to move a clincher base of the clincher unit up and down and to actuate a clincher mechanism.
In order to drive the respective units with the exclusive drive motors on the respective units as described above, sensors arranged in respective portions detect signals at the time of termination of clamping by the clincher unit, termination of striking of a staple by the driver unit, and termination of clinching by the clincher unit, and driving and stoppage of the respective drive motors are controlled on the basis of the signals.
As shown in FIG. 12, the control device drives a drive motor m2 of the clincher unit on the basis of a start signal s1, which is given upon arrangement of sheets, in a bound position, to lower the clincher base to clamp between the same and an upper surface of the driver unit the sheets, stops the drive motor m2 of the clincher unit and drives a drive motor m1 of the driver unit on the basis of a sensor signal s2, which is given upon termination of clamping of the sheets, to actuate a driver to strike out a staple toward the sheets, as clamped, stops the drive motor m1 of the driver unit and again drives the drive motor m2 of the clincher unit on the basis of a sensor signal s3, which is given upon termination of striking of a staple, to bend those legs of a staple penetrated through the sheets, along a back surface of the sheets, so as to bind the sheets, drives the drive motor m1, m2 of the both units on the basis of a sensor signal s4, which is given upon termination of clinching, to return and actuate the respective units, and stops the respective drive motor m1, m2 on the basis of HP signals h1, h2 of the respective units to stop the respective units in home positions.
By the way, while according to the related art, at a point of time when clamping by the clincher unit is terminated, the drive motor m1 of the driver unit is driven to perform striking simultaneously when the drive motor m2 of the clincher unit is stopped, and at a point of time when striking is terminated, the drive motor m1 of the driver unit is stopped and the drive motor m2 of the clincher unit is again driven to actuate the clincher mechanism, there is caused a problem that starting generally takes time at the beginning of driving of a motor until the motor reaches a predetermined rotational speed, and a primary operation is not performed during the starting time, so that the necessary time in one cycle of staple binding is lengthened by periods L1, L2, L3 of starting time.